The Brocard–Ramanujan equation n! + 1 = m²

Prove that n! + 1 is a perfect square only for n = 4, 5 and 7, or find a fourth solution.

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1	{
2	"domain": "mathematics",
3	"topics": [
4	"number-theory"
5	],
6	"type": "construction",
7	"also": [
8	"proof"
9	],
10	"source": {
11	"key": "erdos",
12	"name": "Erdős Problems",
13	"url": "https://www.erdosproblems.com/398",
14	"id": "398",
15	"curator": "Thomas Bloom",
16	"poser": "Henri Brocard and Srinivasa Ramanujan",
17	"status": "open",
18	"as_of": "2026-10-20",
19	"catalog": "0521c19bbd38"
20	}
21	}